The present invention relates to an information processing unit. The invention also relates to a technology that the information processing unit uses to establish specific communication with an external unit, for example, to a technology effective for a microcomputer having a communication function.
Many hardware products having an electronic control unit (ECU) have been widely used due to advanced electronic control technologies. For example, in most of vehicles, ships, airplanes, and other moving bodies, an electronic control unit is used to control, for instance, engines and navigation equipment. An information processing unit having a microcomputer (e.g., LSI) is built in such an electronic control unit.
When a hardware product having an electronic control unit (ECU) is to be designed, various tests are conducted at stages, for instance, of prototype production and outgoing inspection for the purpose of verifying the operations of a target to be controlled by the electronic control unit (ECU) and checking for faults in the electronic control unit (ECU). In currently marketed automobiles, for example, a plurality of electronic control units (ECUs) are used to provide engine control and vehicle control. For example, an electronic control unit (ECU) for engine control is equipped, for instance, with a power train control microcomputer. An electronic control unit (ECU) for vehicle control is equipped, for instance, with a chassis control microcomputer that controls an electrically-assisted power steering motor. The microcomputer in the electronic control unit (ECU) is provided with a debug circuit that outputs the results (software execution results and computed data) obtained when a control target device (e.g., engine or motor) is controlled. At stages, for instance, of prototype production and outgoing inspection, data derived from the debug circuit in the microcomputer is transferred to a development unit external to the electronic control unit (ECU) and used to check the operations of the electronic control unit (ECU). A known technology disclosed, for instance, in Japanese Unexamined Patent Publication No. Hei 9 (1997)-44372 adjusts an electronic control unit (ECU) provided for a vehicle by arbitrarily correcting data used for control operations by a microcomputer.
A technology described in Japanese Unexamined Patent Publication No. Hei 9 (1997)-44372 makes it possible to check for improper communication and transfer data between the electronic control unit and a controller before a power supply system switch for the electronic control unit is turned on. A technology described in Japanese Unexamined Patent Publication No. Hei 9 (1997)-44372 makes it possible to prevent erroneous control caused by a communication error and initiate ROM emulation and RAM monitoring upon startup. Another technology described in Japanese Unexamined Patent Publication No. Hei 9 (1997)-44372 relates to a system that has an electronic control unit for providing engine control with a control CPU and a controller coupled to communicate with the control CPU.
In the system disclosed in Japanese Unexamined Patent Publication No. Hei 9 (1997)-44372, the electronic control unit includes an evaluation board and an input/output board. A control CPU is mounted on the evaluation board. Input/output terminals for various signals are mounted on the input/output board. The electronic control unit turns on when an ignition switch is placed in the ON position. When a power switch for the controller is turned on, electrical power is supplied only to the evaluation board in the electronic control unit through the controller.
The above technologies described in Japanese Unexamined Patent Publication No. Hei 9 (1997)-44372 prevent a control target from being erroneously controlled due to an error in the communication between the electronic control unit and the controller. The technologies described in Japanese Unexamined Patent Publication No. Hei 9 (1997)-44372 also make it possible to initiate ROM emulation and RAM monitoring immediately after the power supply system switch for the electronic control unit is turned on.